The invention relates generally to electric discharge machining (EDM). More particularly, the invention relates to EDM die sinking devices exhibiting higher metal removal rates and lower surface roughness than conventional EDM devices.
EDM die sinking has been used to make a variety of metal structures in small volumes. EDM die sinking typically involves placing a workpiece into a tank of fluid such as hydrocarbon-based oil. A die electrode having a mirror image of the desired shape for the workpiece is moved by a ram into close proximity to the workpiece, and an electric pulse is then repetitively applied to the gap between the die electrode and the workpiece to cause electric discharges that remove material from the workpiece. EDM die sinking has the capability of machining difficult metals or alloys without high cutting force and hard tools, which makes the process cost-efficient and less complex than conventional machining techniques. One possible application for EDM die sinking is in the manufacture of airfoil shapes on turbine blades, which are made of heat resistant, nickel-based alloys that withstand the ever-increasing temperatures of steam turbines. These tough alloys present considerable difficulties in part production because the intricate shapes required are difficult to machine, which drives the cost of equipment and operation higher. Although EDM die sinking is an attractive process for machining these alloys, a number of challenges currently limit its use.